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From 37c791a031ece3afeb9c8b023397473a5349f171 Mon Sep 17 00:00:00 2001
From: Vasily Averin <vvs@virtuozzo.com>
Date: Mon, 24 Dec 2018 14:44:52 +0300
Subject: [PATCH] sunrpc: use-after-free in svc_process_common()
commit d4b09acf924b84bae77cad090a9d108e70b43643 upstream.
if node have NFSv41+ mounts inside several net namespaces
it can lead to use-after-free in svc_process_common()
svc_process_common()
/* Setup reply header */
rqstp->rq_xprt->xpt_ops->xpo_prep_reply_hdr(rqstp); <<< HERE
svc_process_common() can use incorrect rqstp->rq_xprt,
its caller function bc_svc_process() takes it from serv->sv_bc_xprt.
The problem is that serv is global structure but sv_bc_xprt
is assigned per-netnamespace.
According to Trond, the whole "let's set up rqstp->rq_xprt
for the back channel" is nothing but a giant hack in order
to work around the fact that svc_process_common() uses it
to find the xpt_ops, and perform a couple of (meaningless
for the back channel) tests of xpt_flags.
All we really need in svc_process_common() is to be able to run
rqstp->rq_xprt->xpt_ops->xpo_prep_reply_hdr()
Bruce J Fields points that this xpo_prep_reply_hdr() call
is an awfully roundabout way just to do "svc_putnl(resv, 0);"
in the tcp case.
This patch does not initialiuze rqstp->rq_xprt in bc_svc_process(),
now it calls svc_process_common() with rqstp->rq_xprt = NULL.
To adjust reply header svc_process_common() just check
rqstp->rq_prot and calls svc_tcp_prep_reply_hdr() for tcp case.
To handle rqstp->rq_xprt = NULL case in functions called from
svc_process_common() patch intruduces net namespace pointer
svc_rqst->rq_bc_net and adjust SVC_NET() definition.
Some other function was also adopted to properly handle described case.
CVE: CVE-2018-16884
Upstream-Status: Backport [https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/commit/?h=linux-4.9.y&id=37c791a031ece3afeb9c8b023397473a5349f171]
Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
Cc: stable@vger.kernel.org
Fixes: 23c20ecd4475 ("NFS: callback up - users counting cleanup")
Signed-off-by: J. Bruce Fields <bfields@redhat.com>
v2: - added lost extern svc_tcp_prep_reply_hdr()
- dropped trace_svc_process() changes
- context fixes in svc_process_common()
Signed-off-by: Vasily Averin <vvs@virtuozzo.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Andreas Wellving <andreas.wellving@enea.com>
---
include/linux/sunrpc/svc.h | 5 ++++-
net/sunrpc/svc.c | 9 ++++++---
net/sunrpc/svc_xprt.c | 5 +++--
net/sunrpc/svcsock.c | 2 +-
4 files changed, 14 insertions(+), 7 deletions(-)
diff --git a/include/linux/sunrpc/svc.h b/include/linux/sunrpc/svc.h
index 102c84dcc11a..63eed9ac8fd7 100644
--- a/include/linux/sunrpc/svc.h
+++ b/include/linux/sunrpc/svc.h
@@ -291,9 +291,12 @@ struct svc_rqst {
struct svc_cacherep * rq_cacherep; /* cache info */
struct task_struct *rq_task; /* service thread */
spinlock_t rq_lock; /* per-request lock */
+ struct net *rq_bc_net; /* pointer to backchannel's
+ * net namespace
+ */
};
-#define SVC_NET(svc_rqst) (svc_rqst->rq_xprt->xpt_net)
+#define SVC_NET(rqst) (rqst->rq_xprt ? rqst->rq_xprt->xpt_net : rqst->rq_bc_net)
/*
* Rigorous type checking on sockaddr type conversions
diff --git a/net/sunrpc/svc.c b/net/sunrpc/svc.c
index 272c34551979..eea18a124e4f 100644
--- a/net/sunrpc/svc.c
+++ b/net/sunrpc/svc.c
@@ -1137,6 +1137,8 @@ void svc_printk(struct svc_rqst *rqstp, const char *fmt, ...)
static __printf(2,3) void svc_printk(struct svc_rqst *rqstp, const char *fmt, ...) {}
#endif
+extern void svc_tcp_prep_reply_hdr(struct svc_rqst *);
+
/*
* Common routine for processing the RPC request.
*/
@@ -1166,7 +1168,8 @@ svc_process_common(struct svc_rqst *rqstp, struct kvec *argv, struct kvec *resv)
clear_bit(RQ_DROPME, &rqstp->rq_flags);
/* Setup reply header */
- rqstp->rq_xprt->xpt_ops->xpo_prep_reply_hdr(rqstp);
+ if (rqstp->rq_prot == IPPROTO_TCP)
+ svc_tcp_prep_reply_hdr(rqstp);
svc_putu32(resv, rqstp->rq_xid);
@@ -1312,7 +1315,7 @@ svc_process_common(struct svc_rqst *rqstp, struct kvec *argv, struct kvec *resv)
return 0;
close:
- if (test_bit(XPT_TEMP, &rqstp->rq_xprt->xpt_flags))
+ if (rqstp->rq_xprt && test_bit(XPT_TEMP, &rqstp->rq_xprt->xpt_flags))
svc_close_xprt(rqstp->rq_xprt);
dprintk("svc: svc_process close\n");
return 0;
@@ -1439,10 +1442,10 @@ bc_svc_process(struct svc_serv *serv, struct rpc_rqst *req,
dprintk("svc: %s(%p)\n", __func__, req);
/* Build the svc_rqst used by the common processing routine */
- rqstp->rq_xprt = serv->sv_bc_xprt;
rqstp->rq_xid = req->rq_xid;
rqstp->rq_prot = req->rq_xprt->prot;
rqstp->rq_server = serv;
+ rqstp->rq_bc_net = req->rq_xprt->xprt_net;
rqstp->rq_addrlen = sizeof(req->rq_xprt->addr);
memcpy(&rqstp->rq_addr, &req->rq_xprt->addr, rqstp->rq_addrlen);
diff --git a/net/sunrpc/svc_xprt.c b/net/sunrpc/svc_xprt.c
index 064f20bb845a..42ce3ed21637 100644
--- a/net/sunrpc/svc_xprt.c
+++ b/net/sunrpc/svc_xprt.c
@@ -510,10 +510,11 @@ static struct svc_xprt *svc_xprt_dequeue(struct svc_pool *pool)
*/
void svc_reserve(struct svc_rqst *rqstp, int space)
{
+ struct svc_xprt *xprt = rqstp->rq_xprt;
+
space += rqstp->rq_res.head[0].iov_len;
- if (space < rqstp->rq_reserved) {
- struct svc_xprt *xprt = rqstp->rq_xprt;
+ if (xprt && space < rqstp->rq_reserved) {
atomic_sub((rqstp->rq_reserved - space), &xprt->xpt_reserved);
rqstp->rq_reserved = space;
diff --git a/net/sunrpc/svcsock.c b/net/sunrpc/svcsock.c
index 33f599cb0936..fd7fbe91955e 100644
--- a/net/sunrpc/svcsock.c
+++ b/net/sunrpc/svcsock.c
@@ -1195,7 +1195,7 @@ static int svc_tcp_sendto(struct svc_rqst *rqstp)
/*
* Setup response header. TCP has a 4B record length field.
*/
-static void svc_tcp_prep_reply_hdr(struct svc_rqst *rqstp)
+void svc_tcp_prep_reply_hdr(struct svc_rqst *rqstp)
{
struct kvec *resv = &rqstp->rq_res.head[0];
--
2.20.1
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